Nitric oxide (NO) is a gas that, when inhaled, acts to dilate blood vessels in the lungs, improving oxygenation of the blood and reducing pulmonary hypertension. Because of this, nitric oxide is provided as a therapeutic gas in the inspiratory breathing gases for patients with pulmonary hypertension.
However, as NO reacts with oxygen to form nitrogen dioxide (NO2), NO2 can be formed when air is present in the NO delivery conduit. NO2 is a toxic gas which may cause numerous side effects, and the Occupational Safety & Health Administration (OSHA) provides that the permissible exposure limit for general industry is only 5 ppm. Thus, it is desirable to limit exposure to NO2 during NO therapy.
One method of administering NO is through the delivery of a small pulse of a NO-containing gas through a nasal cannula or other conduit. However, the time between successive pulses of therapeutic gas can provide an opportunity for NO and oxygen in the conduit to react to form NO2.
Furthermore, nasal cannulas for portable NO delivery devices may be disconnected intentionally or inadvertently during administration of NO therapy. Such disconnections interrupt therapy and may introduce air into the nasal cannula, which may lead to NO2 formation.
Accordingly, there is a need for new methods and apparatuses for preventing formation of NO2 in the delivery conduit of a nitric oxide delivery apparatus.